ME. GASSIOT ON THE STEATIEICATIONS IN ELECTEICAL DISCHARGES, 
rig. 1 . 
142 
72 Fig. 1 represents a tube 22 inches long, If inch internal diameter . 
the wires a, 5 are 19 inches apart; sufficient mercury remains in the tube 
to corer the lower wire, and in this manner one termmal is a wu-e ot 
platinum and the other a surface of mercniT- The tube when used m 
suspended by a string. In this apparatus, with a smgle ceU of the mtnc 
acid battery, particularly clear and distinct large cloud discha^es are 
obtained, leaving a dark band of 14 to 15 inches m length. IVTien a 
magnet is presented a little above the surface of the mercury, which m 
this apparatus 1 always made the negative terminal, the blue-tongue 
discharge is produced in a most brilliant and beautiful manner, while 
at the same time the cloud-like stratifications from the positive 
brought down the tube. By manipulating with a magnet, the h ue 
tongue can be made to extend up the tube, illuminating the side of the 
glass wherever it impinges with the phosphorescent blue rays. In tffis 
tube the vapour of mercury rises very rapidly; condensing on the sides 
of the glass, the condensation can be easily removed by the liqind 
mercury. In this tube, moreover, the redness does not appear on t e 
surface of the negative mercury, which is covered with a bright lambent 
73. Fig. 2 is another form of a vacuum-tube, 10 inches long, 1 inch 
internal diameter, in which each of the platinum wil-es a and i can be 
covered with mercuiy, so as to permit the surface of the metal to be 
used for both terminals at the same time. With 
one terminal of mercury and the other of wire, 
the white-tongue discharge is very distinct, and 
either with this arrangement or with both termi- 
nals of mercury, the blue phosphorescent dis- 
charge from the negative is shown in a very 
marked manner. When a horseshoe magnet is , ,i + oGnr.' nve 
presented towards the cloud-like stratifications in this tube fce 
attracted towards the magnet when the latter is approached m one 
repelled when presented in another. I shall, in the coui-se of this commim r ation ha« 
occasion to refer to the form which this peculiar discharge assumes when the shape 
the negative terminal is altered. j i 
74 I have already stated (68) that in some instances several seconds elapsed du ^ 
which discharges were made without producing any luminous 
ultimately appearing when the discharges had been further continued. The fo 
experiment shows, that with the wire terminals the stratifications aie much 
by the particular state of the negative terminal, while that of the positive oes no 
fiuence them. Fig. 3. In this tube four whes, n, o', h i' are hermetically 
«' were alternately attached to the positive termmal of the coil, and I, I to 
Eig. 2. 
